Telemetering device



w"eb, 2S, 952

POLIN TELEMETERING DEVICE Filed March 24, 1947' 3 Sheets-Sheet 1 Feb 26, i932 H. s. POUM 2,587,223

TELEMETERING DEVICE Filed March 24, 1947 3 Sheets-Sheet 2 ifm i541 e 145 M13 M? 7&6 IM 157' wue/wt-o/z/ Filed March 24, 1947 H. S. PGI-IN TELEMETER'ING DEVICE 3 Sheets-Sheet 5 Shim/man Patented Feb. 26, 1952 NETE@ iayii Prthliiiwi @FFME TELEMETERING DEVICE Herbert S. Polin, Rio de Janeiro, Brazil, assignor to Audience Computing System, line., New York, N. Y., a corporation of New York Application March 24, 1947, Serial No. 736,705

(Cl. Z50- 2) 8 Claims. l

The present invention concerns apparatus and methods in the eld of telemetering.

It is an object of this invention to provide means to determine data and indicate the summation thereof as a whole or selectively'in order to yield desired information.

It is an object of this invention to provide means whereby quantitative information of thc total number of outlying receiving points adjusted to a predetermined signal is indicated at a central point.

It is an object of this invention to provide means to determine the total number of radiobroadcast receivers that are active at a given time. 1 It is an object of this invention to provide means arranged to indicate automatically, at

',some central point, the total number of radio L ,receiving stations in a selected area that are 1 means whereby the operator of a radio set may vote or indicate an individual preference.

In the field of radio-broadcasting it is desirable for many reasons to know the number of listeners to the program. It is usually desirable to eliminate programs which have little or no appeal and select those which have a wide range of acceptance. Again the value of any advertising medium depends directly upon the public it reaches. Many newspapers and magazines have advertising rates which are a function of their circulation. Many radio programs are paid according to the number of listeners or relative rating they enjoy. These listeners are now counted by the poll method, which is laborious, costly and in many cases is probably not accurate to a desirable number of signicant iigures. The sampling taken is assumed representative and every effort is no doubt exerted to make it so. but the methods now employed make a reasonably accurate determination prohibitive in cost, Telephoning, written communication or personal canvass leave much to be desired. Even an elaborate recording device connected to the radio receiver in a selected group of homes which prints a time base record registering the ofi and "on hours of the individual set as well as the station Selected for each on" period is open to some of the serious objections of the other methods as well as objections peculiar to it. A service man periodically removes the record and the data are tabulated from the records of all the recording machines outstanding. Such apparatus is costly, requires constant servicing for collection of records, the installation of new data rolls or charts as well as repair. Such a system by its very nature must be quite limited and its accuracy can be no better than the representa- .tiveness of the sample selected. With such systems a small error is magnified by a multiplier which is the ratio of the total number of receivers to those thus specially equipped.

The present system here disclosed is inexpensive to install, may be incorporated as an integral part of a new radio receiving set, or may be installed as an auxiliary unit of an old set. There is no recorded chart and no servicing operation at the receiving set.

The method by which this indication may be achieved is diagrammatically illustrated in the accompanying drawings which illustrate the diagrammatic layout of the system as a whole. Outlying radio receiving sets are each equipped with a device tuned to a selective modulation or signal on the carrier frequency of any transmitting station. This device, which may be a type of vibrating reed relay, is identified with a load of electrical characteristic, such as resistance, inductance, capacitance, phase shift, etc., and with a conductive path whereby, upon receipt of the predetermined signal by radio, the vibrating reed relay closes a circuit which applies the aforesaid electrical load across the conductive path. The sets are connected with power lines which are connected to substations through suitable meters. Assuming that the load applied to the line by the action of the relay be resistance and that the meter be an ammeter, then, for the time period that the transmitting station emits the signal to which the relays are responsive, the ammeter will register, in addition to its normal load, the additional short duration or transient load synchronous in time and duration with the transmitted signal. The increment of change between the normal load and the additional load responsive to the transmittal signal may be calibrated in number of receiving sets, and thus, the diiierence in load may give a direct indication of the number of receiving stations tuned to i a particular transmitting station at a particular time.

A citys power service is normally composed of a number of substations, each serving a particular district, and it is the plan of the system herein proposed to transmit the information registered at each substation to a central point. At this point the load at each substation, responsive to the signal frequency, may be totalized. A convenient method for measuring the change responsive to the signal frequency is by the use of a cathode ray oscillograph.

Since load perturbations are normally occurring constantly in any power line, and since only those perturbations responsive to the signal frequency are to be measured, discrimination is obtained by a coding plan related to a time axis. This is accomplished by feeding into the oscillograph the total of the loads registered at each of the substations and by applying, in the oscillograph, an artificial load of equal and opposite chai:- acteristic. As the load varies iortuitously from minute to minute, or from hour to hour, the artificial load of opposite sign varies with it. When, however, the radio transmitting station emits the signal frequency in a predetermined coded pattern, the artificial load is maintained constant and\the oscillograph registers the increment of change produced by the signal frequency. Simultaneously, the timing circuit of the oscillograph has impressed upon it the pattern of the signal frequency code.

The system described has been illustrated as applied to a power line. It is obvious, of course, that any conductive path would serve to transmit the desired information and a telephone line, or any other convenient conductor would serve.

While one form of increment indication as registered by an oscillograph or the like involves the summation of power represented by a multiplicity of resistance loads, it is equally obvious that capacity or inductance, or both, may serve as the signal-responsive load, with appropriate instruments in each instance, for their measurement. The unique requirement for the system is that the load be of a character capable of being summed. that is, that each additional unit applied to the transmission line shall contribute a proportional change modifying the total of its 7.-,

characteristic upon the line. rIhus, the load may consist of a phase-shifting circuit applied to the transmission line or, the load may consist of a combination of inductance, capacity, resistance, phase-shift, etc.

i The specific parts comprising the various units may be described as follows:

1. Transmitter.-At the radio transmitting station the apparatus consists of a modulator, for example a lO-cycle per second low frequency signal unit. The modulator is equipped with a coding key of predetermined pattern. By telephone line or similar circuit, this modulator is connected with the oscillograph in the central station, or totalizing center. 1t may also be desirable to locate the coding key at the totalizing center.

2. Totalzzz'ng centen-The equipment here conslsts of telemetric lines from each of the substations with the information derived from these lines fed into a cathode ray oscillograph. The cathode ray oscillograph includes a timing circuit and a bucking circuit. The master key of the modulator is introduced into the oscillograph circuit in such form that it registers its pattern upon the timing circuit and simultaneously disconnects the automatic follow-up of the bucking circuit. Thus the artificial load is maintained in synchronous opposition to the normal load until the instant that the modulator signal is initiated. For the short duration of this signal pattern, the artificial load is not affected by the actual load. As the modulator coded pattern terminates, the artificial load again functions in automatic opposition to the normal load.

It is desirable to have a recording system associated with the oscillograph.

3. Substatio1zs.-The equipment at each substation consists only of a means for transmitting the load changes, as they occur, to the totalizing center. Many systems for transmitting information telemetrically are known in the art, and any of these will serve.

4. Radio receivers-Each radio receiving set must have included in its output a discriminatory device responsive to a particular signal. Since one feature of the totalizing system here described is its capacity to indicate separately the number of receivers tuned simultaneously to broadcasting stations operating on dinerent frequencies, it is advantageous that the signalresponsive device oe included in the audio rather than in the radio-frequency elements of the receiving set. The signal unit may comprise a simple vibrating reed relay, with or without amplification (tuned to the lO-cycle per second signal mentioned in 1 above). The relay, responsive to the broadcast signal frequency, closes a circuit which includes the signal load, i'or example, a one watt resistance.

The cycle of operation of the system as a whole is as follows; Assume that 100,000 receiving sets are so equipped in a given locality. During the broadcast, the totalizing center desires to know how many sets are tuned to a particular broadcasting station. The coding key is depressed and the transmitting station uncer test transmits the low rrequency signal modulation during its program. ('i he low frequency signal is of short duration and in a frequency range substantiaily outside of acoustical interference.) As the transmitting radio station broadcasts the signal frequency, the oscillograph at the totalizing center registers the increment of change in the standard load, and iinds that the peak, synchronous in time with the signal frequency, shows an increase of 20 kilowatts. This indicates that of the total 100,000 stations equipped i'or this service, 20,o00 were tuned to the station under test.

Another feature of described system is the possibility of utilizing the system as a voting device. By inserting a. switch in each receiving set whereby the listener may apply the signal load across the line, each listener, in response to a broadcast questionnaire, may register his preierence. This switch also may be oi' a type that transmits a coded pattern.

In the drawing like numbers refer to like parts throughout.

Figure 1 is a schematic diagram of an entire system employing the invention.

Fig. 2 is a fragmentary circuit diagram of a supeiheterodyne receiver equipped with one form of the invention.

Fig. 3 is a schematic layout of the totalizing center and shows one general method of obtaining the voting differential.

A standard broadcast receiver |00 is connected to power lines |0| and |02 by the normal plug leading from the primary |03 of power supply transformer |04. Secondary |05 leads to lament |06 of rectifier tube |07 of the type known as NIT-74. Secondary |08 has each end connected to plates |09 and ||0 of tube |07 by wires and ||2 respectively. A central tap ||3 is taken ofi secondary |08 and connected to wire llfi of heater secondary ||5 at junction |13 by wire |Il. Cathode ||8 is connected to junction ||9 and power supply filter choke inductance |20 by wire |2|. Junction ||9 is connected to wire H4 through filter condenser |22 by wire |23.

rI'he power amplifier comprises tubes |21i and |25 of the type known as VT-GG connected in push-pull. Plates |26 and |21 are connected one to each end of primary |28 of output matching transformer |29 by wires |30 and |3|. Secondary |32 is connected to voice coil |33 of speaker |34 by wires |35 and |35.

A loaded inductance |31 is connected in parallel with primary |28 by wires |39 and |40 at junctions |ll| and |42. A metallic reed |43 is positioned on mounting |88 in such a manner that it lies within the field of inductance coil |37. Reed |53 is weighted at its free end by adjustable weight |56 which controls its frequency. A frequency of ten, cycles per second has been selected as serviceable in most cases. The vibration is inaudible save as it may be added to or subtracted from other frequencies in the audible range. It is recognized that the frequency response of a commercial receiver may well be poor at ten cycles per second. Nevertheless, although a. ten cycle signal may be considerably attenu ated after th e original modulated carrier has been detected, some of this signal will appear in the output of the receiver. This factor of attenuation should be taken into account in the design of reed |43, and the moment of inertia of the reed |l3 should be such that the attenuated signal will still effect a build up of oscillation of the reed. Reed |133 extends freely between a pair of contacts |85 and |66. There is sufficient space between reed |153 and contacts |45 and |86 to require a three to five cycle oscillatory build-up before the amplitude of vibration of reed |113 is such that it closes the circuit and touches contact |85 or |86. A random pulse will not close the circuit.

Terminal |i7 is mounted on the base of reed |63 and is connected at junction |48 to line |81 by wire |49. Contacts |45 and |46 are joined by wire |50 containing junction |5| and connected to junction |52 by wire |53. Junction |52 is connected to junction |55 on line |82 by wire |56 containing resistance |57. Resistance |57 preferably has a rating of about one watt. Junctions |47 and |52 are connected by wire |58 containing manually operated switch or voting key Home receivers |68, or any similar device concerning which data is desired or by which, alone or in conjunction with other apparatus, data may be determined, are parallel across local lines These local lines lead to meters |68 and |65 in substations |66 and |67. Substations |66 and |67 together with others are connected by feeder lines |68, |69, |78, |7|, |72, |73, |74 and |75 to main station generator line |76 and |77 through main station meters |78, |79, |86 and |8|.

A modulator reading and coding device |82 is connected in the line and contains a line ammeter |83 shown in Fig. 3 has its coil connected in line |77 and may be in series or across a shunt in the normal manner. Modulator |82 is connected to a suitable voltage amplifier |89 which is connected in turn to oscillograph |85 and transmitter |86. Modulator |82 is connected to oscillograph |85 and transmitter |86 by wires diagrammatically suggested in Fig. l.

Modulator |82 contains a rectier |87 across main station lines |75 and |77 and an ammeter |83 in series with said line. Ammeter |83 is connected mechanically by selsyn |88 to movable arm |89 of rheostat |90. Selsyn |88 is connected or disconnected under the control of the master modulator key. The pivot |9| of arm |89 is connected to the positive terminal of battery |92. The negative terminal of battery |92 is connected to the negative side of rectifier |87 by wire |93.

The movable end of arm |89 contacts resistance |99 which is connected to the positive side of rectier |87 through resistance |95 by wire |96. The voltages of battery |92 and rectifier .the instant of disconnection of selsyn |88 and ammeter |83 as determined by the master modulator key device |82 and so slightly project the curve of the value it transiers.

Voltage amplifier |84 has one side connected to junction |98 with wire 93 by wire |99. The input signal to ampliiier 181i is obtained by wire 206 which adjustably contacts bridge resistance |95. The output of voltage amplier |88 is connected to oscillograph and serves to deflect its beam from the central zero position in the manner indicated.

The operation of the system is as follows:

The 'vibrating reed |173 and its associated equipment are preferably installed at the factory. When receiver |60 is operating the magnetic field of inductance |37 will vary with the amplirled voice current in transformer-|29 and Voice coil |33. The random accelerations experienced by reed |63 cancel out and it does little more than quiver. By random accelerations are meant those signals having a frequency suiiciently close to the natural period of reed |93 to exert a force thereon. The inertia of reed |53 is such that a random pulse normally is not of sucient duration to cause the reed |63 to move enough to close the circuit at either contact |45 or |86. Should it be found that in a given frequency range such random pulses do close the reed circuit it will be necessary to increase the inertia of reed |63 or change its natural resonant fre qucncy. In the usual case random accelerations accelerate and decelerate the reed |93 as they are in and out of phase with preceding random accelerations and the inertia oi reed |43 is so chosen that the time required to attain a sufficient movement to close contacts |45 and |116, while only a small fraction of a second, is long enough to permit both accelerating and decelerating random signals to act on reed |43 and by opposing each other substantially cancel out. An occasional random build up which causes reed |63 to infrequently close the circuits of contacts |65 and |116 may be disregarded as the chances of its occurrence at the instant of registration are small and if so the chance that such random data will not be detected by comparison and check are still smaller. When the central broadcasting station modulation control key is pressed the ten cycle note is radiated from the antenna of transmitter |83 and appears on the magnetic neld of inductance |87 as a ten cycle ripple. In about half a second or less the amplitude of vibration of reed U33 builds up and the reed |43 makes contact with one only or both oi contacts |65 and |86 in sequence. This action closes the circuit of wires |89 and |58, placing resistance |57 across local lines |0|, |02. While this circuit is closed resistance |57 draws one watt of power. Of course any other suitable value may be chosen as desired. Again a suitable capacitance, or inductance or phase shifting circuit may be substituted for resistance |57. This action occurs only in those receivers 96 tuned to the station sending out the ten cycle note on its individual frequency. Ail the resistors |57 of all such sets draw a watt each. As noted this may be reactive power with the current leading or lagging if desired.

The meters |64, |65, etc., at the Various sub stations show the power drawn by the local lines. Main station meters |18, |19, |80, |8|, etc. show the same data. Ammeter |83 fluctuates with the total load of the entire station or that portion over which the desired data is being collected. Selsyn |88 turns arm |89 according to the nuctuations of rmeter |83 and introduces more or less of resistance |911 into the balanced circuit of rectifier |81 and battery |92 as ammeter |83 falls or rises.

The output of rectifier |81 varies with the load on line |16, |11 and is balanced by the output of battery |92 as controlled by the in-circuit portion of resistance |94. Lead 200 from the input portion of voltage amplifier |34 is positioned at the Zero point of bridge resistance |95, so that no signal is carried by wire '.299 while the arm |89 fluctuates under the control of ammeter |83. The trace or light point 29| of oscillograph |85 rests at Zero position.

When the broadcasting station master modulator control key is pressed the selsyn control |88 is disconnected and the arm |89 drifts very slightly in the direction of the last movement of the selsyn |88, thus projecting the curve of main line current in the direction of its trend at the instant of disconnect, a small amount. Any subsequent increase in the output of rectifier |81 will be unopposed by the momentarily steady output of the circuit of battery |92 and resistance |94 and the difference will be amplified by voltage amplifier |811 and appear on oscillograph as a displacement of trace or light point to the left or upward as the case may be. The amount of displacement will vary directly with the unopposed voltage and may be taken as a measure of the summation of the resistance loads |51 introduced by the properly tuned receivers |00. A reading of twenty k. w. means about twenty thousand receivers are tuned to the signaling station. Much random error may be eliminated by averaging a series of readings. Drastic fluctuations are in a measure smoothed by selsyn |88 and condenser |91.

It may be desirable not to have the oscillograph |85 connected at all times. If so the master modulator key should be connected to perform the following functions:

1. Disconnect selsyn control |88.

2. Connect rectiner |81 to bridge circuit.

3. Connect D. C. battery to bridge circuit.

4. Connect voltage amplifier' |86 to the bridge circuit at point of balance in resistor |95.

This device offers wide application and various embodiments of the invention may be made without departing from the spirit thereof.

The device functions by measuring increments of load at a chosen instant. This increment may be resistance or reactance. Random error caused by other loads being placed upon or removed from the line is caused to cancel itself as outlined above. Any error may be reduced by a series of readings closely related in time.

I claim: l. In a telemetering system, transrntipg means propagating radiant energy/*gat a fixed cha'ir frequency, means coupled to said transmitting means for modulating' said fixed carrier frequency with a predetermined slglillfllly a pigralltmgfpiepelyinaineans adjust-ably tunable to said carrier frequency, an electrical network, each of said plurality of receiving means including an impedance and switching means coupled to said impedance and to said electrical quency network, said switching means including means responsive to said signal frequency and coupling said impedance to said network when said carrier frequency is modulated by said signal frequency, indicating means coupled to said electrical network, said indicating means having a datum indication, variable bucking load means coupled to said indicating means and to said electrical network, said bucking load means opposing electrical variations in said electrical network to maintain said indicating means at its datum indication when said carrier frequency is not modulated by said signal frequency, said bucking means including means disconnecting said bucking means from said electrical network when said carrier frequency is modulated by said signal frequency.

2. A system as claimed in claim 1 wherein each of said receiving means includes means for demodulating said carrier frequency to reproduce said signal frequency.

3. A system as claimed in claim 1 wherein said transmitting means includes means se/lectivelyw` modulating said carrierfrequency with, axyariable intere--. dansend/iam.- .aises signainer.

4. Asystem as claimed in claim 1 wherein said switching means includes means mechanically resonant at said signal frequency.

5. A system as claimed in claim 1 wherein said switching means comprised a relay having at least two contacts and a movable reed suspended between said contacts, said reed being mechanically resonant at said signal frequency and having such inertia that several cycles of oscillations at said signal frequency are required to cause the amplitude of mechanical oscillation of said reed to become sufficient for the reed to touch said contacts.

6. A system as claimed in claim 1 in which said indicating means includes oscilloscope means.

7. A system as claimed in claim l wherein said bucking load means is so constructed as to have sufficient inertia to continue to affect the datum indication of said indicating means after said bucking load is disconnected from said network in the same manner it was affecting said indication immediately before said bucking load was disconnected.

8. A system as claimed in claim 1 wherein said bucking load comprises metering means, a variable resistance, and a selsyn coupled to said metering means and to said variable resistance.

HERBERT S. POLIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,944,315 Clapp Jan. 23, 1934 1,990,489 Hopkins Feb. 12, 1935 2,063,610 Linsell Dec. 8, 1936 2,092,119 Hopkins Sept. 7, 1937 2,092,120 Hopkins Sept. 7, 1937 2,096,109 Hopkins Oct. 1l, 1937 2,140,016 Kautter Dec. 13, 1938 2,188,165 Thomas Jan. 23, 1940 2,206,702 La Pierre July 2, 1940 2,213,886 Potter Sept. 3, 1940 2,397,562 Potter Apr. 2, 1946 2,513,360 Rahmel July 4, 1950 

